engleski

Iridium Catalyzed Allylic Substitutions: Mechanism and Catalysts Improvements by Rational Design

The key allyl intermediate and resting state of the iridium catalyst in the asymmetric allylation of amines will be presented. Active allyl intermediate was isolated and characterized by X-ray diffraction. The intermediate is an octahedral complex where allyl is 113-ligand. Stochiometric nucleophilic attack of aniline on the complex was studied. The complex was active as a catalyst for allylic ammination. The resting state is a complex of the metallacyclic catalyst with the olefinic unit of the allylamine product. The species containing N-phenyl cinnamylamine complex have been isolated in pure form Its mimic, a related ethylene complexes have been prepared on multigram scale (equation 1). The simple synthesis of these metallacyclic iridium complexes gives rise to a single-component, highly active and enantioselective catalysts for the asymmetric allylic substitutions.Kinetic data on the overall catalytic cycle for the allylic ammination will be discussed. The rates of the catalytic reaction are first-order in allylic carbonate, amine, and catalyst, and inverse-first order in product. This combination of data, along with the observation that the resting state is stable toward 1.5 equiv of allylic carbonate, implies that the reaction of the iridium(I) species with the allylic carbonate is reversible and endoergic, and that this intermediate reacts with the nucleophile to form product.

mechanistic studies, nucleophilic substitution, iridium,

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